I'm trying to replicate something I have been able to complete with Excel for reconciling high-value/theft items in a supermarket (cigarettes) in Python.

Currently, in Excel it looks something like this:

1. The user enters any additional cigarettes they have taken from the warehouse storage and brought to the sales area.
2. At the end of the day, the user counts the cigarettes in the cabinet (end of day).
3. The spreadsheet then calculates how many packs have been taken from the cabinet:
   (Start of Day QTY + Additions) - End of Day = sold
4. This result is then compared with the sales that have gone through the POS system. Differences are displayed.
5. When ready, the user selects a button that clears the form - but copies the end-of-day figures over to the start of day QTY.

My progress so far is slow - I have been able to read in sales data from POS and clean it up for use, but am struggling with where to start for the example above.

Any advice or pointers on where to start or look would be appreciated. Is this overly complicated to achieve in python? Are there easier alternatives (other than excel haha)?